Field of the Invention
This invention relates to high power laser systems of the type which, typically, operate at up to and over 500 watts of average power in the high average power mode and up to and over 75 joules per pulse in the high energy mode, and has a lens system which is constructed of several individual pieces in order to form an integral lens holding system that maximizes the useful lens aperture. Such structures of this type, generally, allow a laser/fiber user to quickly change lenses, while simultaneously maintaining optical alignment when the lens is replaced.
Laser materials processing as known in the art and as used herein refers to the performance of materials processes such as cutting, welding, drilling and soldering using a high power continuous wave or pulsed laser beam. The average power of a high power laser beam may range from as little as approximately 1 watt to hundreds of watts. As user selects the specific power of the beam on the basis of the particular process being performed.
Known art describes transmitting a laser beam from a laser source in the vicinity of a workpiece by means of an optical fiber. For example, an apparatus and method for injecting a power laser beam into an optical fiber for transmission therethrough are described in commonly assigned U.S. Pat. Nos. 4,564,736, 4,676,586 and 4,681,396, entitled "Industrial Hand-Held Laser Tool and Laser System", "Apparatus and Method for Performing Laser Material Processing Through a Fiber Optic" and "High Power Laser Energy Delivery System", respectively.
Transmitting a laser beam through an optical fiber to an output coupler also is known. Such an apparatus is described in commonly assigned U.S. Pat. No. 4,799,755, entitled "Laser Material Processing with a Lensless Fiber Optic Output Coupler". In the apparatus described in U.S. Pat. No. 4,799,755, lens systems are not utilized in an output coupler. Rather, a fiber injecting lens is selected to have a focal length of sufficient length to enable the use, for materials processing, of the diverging beam emitted at an output end of the fiber without a need for a beam focusing lens-type output coupler.
An output coupler having a lens system therein for focusing a laser beam transmitted thereto through an optical fiber is disclosed in commonly assigned U.S. Pat. No. 4,844,574, entitled "Optical Fiber Output Coupler for a Power Laser". The apparatus described in U.S. Pat. No. 4,844,574, includes a lens system that compensates for adverse affects of fiber transmission in order to improve focused spot power density of the fiber transmitted beam. The lens system illustrated in U.S. Pat. No. 4,844,574 causes the beam to undergo focusing action within the output coupler. In high power beam transmission, however, focusing a beam within a coupler is undesirable because the focused beam may cause air in the coupler to ionize. The ionized air will deflect the high power laser beam passing through the coupler and the beam may impinge against and damage components within the coupler. At column 12, lines 9-16, of U.S. Pat. No. 4,844,574, it is pointed out that a plano-concave or double concave lens, which will provide a diverging beam, could be utilized, thereby eliminating problems related to focusing the beam within the coupler.
Still other known laser material processing systems utilize lens systems at an output of laser source. Such systems are described in U.S. Pat. Nos. 3,419,321 and 4,275,288, entitled "Laser Optical Apparatus for Cutting Holes" and "Apparatus for Machining Material", respectively. In each of these systems, optical fibers are not utilized. Therefore, since a laser source generally is a stationary system, at least during a materials processing operation, lenses are aligned with the beam directing output by the laser source. But mobility of such systems is limited.
Further, lens holding mechanisms are well known in the art. Exemplary of such prior art lens holding mechanisms are U.S. Pat. Nos. 4,868,361 and 4,997,250, respectively entitled "Coupling Device for High Power Laser Beam Transmitting Optical Fibers" and "Fiber Output Coupler with Beam Shaping Optics for Laser Materials Processing System". While these systems have met with a modicum of success, they are made up, of necessity, of numerous parts. Due to the shear number of these parts and their complex arrangement, all necessary to properly transmit the beam, they do not necessarily maximize the useful lens aperture.
Still further other lens holding mechanisms such as spring loaded arm configurations which grasp the lens, round annular threaded rings such as those found on camera lens assemblies, adjustable lens holders using dual bars, "V-blocks", and adhesive holders have been employed. Again, none of these lens holding mechanisms maximize the useful lens aperture of the fiber optic output coupler. Therefore, a more advantageous lens holding system, then, would be presented if the lens aperture could be maximized.
It is apparent from the above that there exists a need in the art for a lens holding system for fiber optic output couplers which is light weight through simplicity of parts and uniqueness of structure, and which at least equals the beam focusing characteristics of the known lens holders, but which at the same time is capable of maximizing the useful lens aperture. It is a purpose of this invention to fulfill this and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure.